Piezoelectric crystal holder



Jan. 27, 1942- R. BECHMANN ET Al.

PIEZOELECTRIG CRYSTAL HOLDER Filed Oct. 17, 1939/1,Illlllllllllllll/ll/ll/IA 2 Sheets-Shea*I l INVENTORS RUDOLF BECHMANNWILHELM SCHNE/DER /wM-Vl/ ATTORNEY.

Jan. 27, 1942. 'R BECHMANN TAL 2,270,922

Filed Oct. l'l, 1959 2 Sheets-Sheet 2 ff/////////////////////,yA

INVENTORS RUDOLF BECHMA NN BY WIL HEL SCHNEIDER ATTORNEY.

Patented Jan. 27, 1942 UNITED STATES PATENT OFFICE BIEZOELECTRIC CRYSTALHOLDER Application October 17, 1939, Serial No. 29957912 In GermanySeptember 12, 1938 (ci. 1v1-327) 7 Claims.

This invention relates to a new and useful mounting or holder forpiezo-electric oscillators and resonators. An object of this inventionis to improve the temperature stability of a quartz crystal holder.

A feature of this invention is the arrangement of circulating a fluidaround the crystal to maintain a substantially constant temperaturethereto,

Even when quartz crystals having low temperature coeflicients are used,the question of temperature stabilization of the quartz crystal isimportant and in many cases it is necessary to insure great constancy orstability of piezoelectric oscillators and resonators. In the operationof a plurality of broadcast stations on one and the same wave length orin the construction of quartz clocks or time pieces, the frequencystability must be of an order of magnitude of 10-s or over. Using quartzcrystals having a temperature coeicient of 1x10-7, the temperatureconstancy must be one-tenth of one degree C., While in extreme cases thetemperature constancy must be up to one-hundredth of one degree C.

It is a known fact that thermostats operated by heater elements in anair ambient will insure temperature stability of over one-tenth of onedegree only with relatively elaborate circuit means. Thermostats whichare predicated upon liquids for their operation are far less involvedand difficult in practical use. It is known that liquid baths which areagitated by stirring means can be kept at a constant value without anygreat difficulty up to one-hundredth of one degree C. In fact, by theuse of liquid thermostats of this kind, it is possible to establishstable states of temperature in air spaces in which elements to bemaintained at a constant temperature are immersed. One shortcoming ofall temperature regulator or thermostatic devices which are in the formof heat containers is that they require considerable time for heating upbecause the temperature balance or equalization between the enclosure orchamber which is to be kept at a constant temperature by the heaterelements and the means to be regulated or controlled is eiected by thecirculation of air.

According to the invention, the quartz mounting or holder is to be keptat a stable temperature by the use of a circulating liquid thermo-devicewhich is directly built in the form of a liquid thermostat in such a Waythat the wall or shell of the quartz crystal mounting directly forms thewater container or chamber or else the inside a liquid bath which iskept at a constant temperature.

This invention will best be understood by referring to the accompanyingdrawings, in which:

Fig. l is a cross-sectional View of a single crystal holder;

Fig. la is a plan view of Fig. l;

Fig. 2 is a sectional View of another embodiment of this invention;

Fig. 3 is a sectional View of a crystal disposed within a hermeticallysealed vessel;

Fig. 4 is a sectional view of a combination of several crystalmountings;

Fig. 5 is a plan view of Fig. 4; and

Fig. 6 is a plan View of a holder for retaining eight crystals which aredisposed in parallel and in series arrangement.

An exemplified embodiment of a quartz crystal mounting which ismaintained directly at a constant temperature by a current of water isshown in Fig. l. The quartz crystal mounting properly so-called isindicated at I and contains a liquid chamber 2 through which the liquidmay be maintained at a stabilized temperature by being circulated bymeans of a pump from any suitable source, the liquid being passedthrough the orifices 3 and 4. To insure better safety against thermalradiation, a heat-insulating coat 5 is placed around the mounting. Thecrystal and the electrode system co-operating therewith are disposed inthe interior of the metallic cylinder I, the crystal being denoted by 6and the two electrodes by 'I and 8. 9 and I0 are insulation disksdesigned to preclude the danger of unnecessary chilling of the electrodesystem from the outside. In order to prevent undue cooling of the liquidiiowing through the admission ducts and kept at a constant temperature,the inlet and outlet ducts are disposed concentrically or co-axially inaccordance with the counter-flow principle as indicated at II and I2. Iland I2 indicate the inlet and outlet pipes or ducts as being arrangedinside each other, -so that there is a chance for the temperaturedifference in the inlet and outlet pipes to become equalized. In orderto promote flow of water under conditions of thorough Contact, the twoinlet and outlet tubes 3 and 4 are arranged tangentially in respect tothe shell of the water container or chamber. As a result, the waterinilux will be tangentially in relation to the water chamber, In orderthat the water circulation may be uniform and regular, no matter whatthe particular position of the mounting illustrated in Fig. l,

mounting is hermetically sealed and is immersed 55 a rib or n system I3is provided in the water chamber 2 designed to impart to the water adesirable twistf A more detailed and special arrangement of the said ribor iin system is shown in Fig. 2 wherein there is shown a thin flatstrip I3 arranged to form a spiral path which surrounds the outside wallof the crystal mounting. The ends of the strip terminate adjacent theinlet and outlet tubes.

Another exemplified embodiment; of the liquid thermostat is shown inFig. 3. The crystal mounting I with the crystal B is disposed inside ahermetically sealed vessel 23. The latter is arranged to have all aroundContact with the flow of liquid, the latter being kept at a stabletemperature. The body or vessel 23 is suspended by means of a neck 24 inthe double-walled cover (21, 28 and 29). The connection between thecover and the vessel preferably consists of a ceramic pipe 2D which haspoor heat conducting properties. The said ceramic pipe piece moreovercontains the two electrode leads brought to the crystal. The body 24 issecured on the double-wall 1, for instance, by the aid of a rubberpacking 25 and a screw joint 26.

The thermal contact or union between the quartz crystal and the mountingof the crystal, itself, in an embodiment as shown in Figs. 1 and 3,should be as perfect and thorough as possible. In this manner, theheating-up period of the thermostat will be fast, as the supply of heatis not by virtue of air convection, but rather by heat conduction by wayof the metallic material. In the embodiment just described, this will beaccomplishable by having the wall of the mounting of the crystal,itself, maintained, at a constant temperature because of the constanttemperature of the circulating liquid. Contradistinct to air thermostatsdelay or baie elements designed to compensate and equalize thetemperature for the heat conduction are undesirable.

Fig. 4 shows a combination of several quartz crystal mountings of thekind shown in Fig. 3 inside a double-walled or jacketed liquid containeror chamber. The liquid is suitably admitted in the same Way as in Fig.3.

Fig. 5 shows a plan view of such an arrangement, with the trough beingin the form of a jacketed cylinder.

Mounting of the kind described by reference to Fig. l according to thisinvention may be assembled and combined in any desired number byarranging the liquid supply means in parallel or in series. 6 shows anexemplified embodiment in which eight quartz crystals are connected withone and the same admission and supply system. In the scheme shown in 6,pairs of crystal mountings are disposed in parallel and in series. Forthe sake of facilitating exchange of units recourse is had to screwunion which is adapted to be speedily opened.

What is claimed is:

l. A piezo-electric crystal holder comprising a crystal located within acasing, an inner wall for said casing which surrounds the crystal, a ribsystem arranged outside said inner wall, a circulating fluid path formedby said rib system which surrounds the crystal and having its path incontact with the inner wall of said casing, and an inlet and an outletat substantially the same point on the outside wall of said casing.

2. A piezo-electric crystal holder comprising a plurality of crystalslocated Within a casing, an inner Wall surrounding each of said crystalswithin the casing, a rib system arranged outside said inner wall, acirculating fluid path formed by said rib system which surrounds thecrystals and having its path in contact with the inner wall of saidcasing, and an inlet and an outlet coaxially arranged at the same pointon the outside wall of said casing.

3. A piezo-electric crystal holder comprising a crystal located within acasing, an inner wall for said casing which surrounds the crystal, a ribsystem arranged outside said inner wall, a circulating Iiuid path formedby said rib system to impart a twist to said iiuid which surrounds thecrystal and having its path in contact with the inner wall of saidcasing, and an inlet and an outlet at substantially the same point onthe outside wall of said casing.

4. A piezo-electric crystal holder comprising a crystal located within acasing, an inner wall for said casing which surrounds the crystal, a ribsystem comprising a at strip arranged to form a spiral path around theoutside of said inner wall, a circulating fluid path formed by said ribsystem which surrounds the crystal and having its path in contact withthe inner wall of said casing, an inlet and an outlet coaxially arrangedat the same point on the outside Wall of said casing and locatedtangential with respect to said uid path.

5. A piezo-electric crystal holder comprising a plurality of crystals, adoublewalled metallic casing for enclosing and maintaining a constanttemperature on said crystals, a Vessel surrounding each one of saidcrystals, each one of said vessels supported by one of the double wallsof said casing, a circulating fluid surrounding said vessels and havingits path in contact with the inner wall of said casing and the outerwalls of said vessels, an inlet and outlet for said circulat ing fluidlocated substantially at the same point on the outside wall of saidcasing.

6. A piezo-electric crystal holder comprising a plurality of crystals, adouble-walled metallic casing for enclosing and maintaining a constanttemperature on said crystals, a vessel surrounding each one of saidcrystals, each one of said vessels supported by one of the double wallsof said casing, a circulating fluid surrounding said vessels and havingits path in contact with the inner wall of said casing and the outerwalls of said vessels, and an inlet and outlet for said circulating uidcoaxiaily arranged at substantially the same point on the outside Wallof said casing.

'7. A piezo-electric crystal holder comprising a crystal, a doublewalled metallic casing for enclosing and maintaining a constanttemperature lor said crystal, a hermetically sealed vessel having a neckportion for enclosing said crystal, said hermetically sealed vesselsupported by one ol the double walls oi said casing at its neck portion,a circulating fluid surrounding said hermetically sealed vessel andhaving its path in contact with the inner Wall of said casing and theouter wall oi said vessel, and an inlet and outlet for said circulatingfluid located at the same point on the outside wall of said casing.

RUDOLF BECHMANN. WILHELM SCHNEIDER.

